Question: 14 Bolt Slide on drum conversion?

Hoplite

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Hey Folks,

Does anyone know if you can bolt on the brake drum ends from a 14 bolt with a slide on drum to the older style that's mounted behind the axle?

Currently I have two full 4.10 FF 14 Bolts sitting in my garage. One has slide on drums but the bearings are shot. The other has good bearings but has the older style drums which are a pain in the rear. Does anyone know if these brake systems can be directly bolt on swaps between the two housings?

I have been wanting to give it a shot but have allot going on. I've been trying to do research to see if it's even possible before I start damaging any seals from disassembly. I've seen in some places that people say yes it's possible, and others they say that it's not possible due to axle lenghts being different. Any input would be greatly appreciated.

Thanks!
 

Schurkey

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Sort-of. JD7, using Hydroboost. JB7 is vacuum-boosted. At least, that's what the '97 Service Manual shows.

In '88, what was later JB7 is listed as "JN7"; big rotors, 2.5" x 13" rear drums, vacuum booster.

I have heard--but not confirmed--that the 3.5" x 13" drums are the slide-ons, mounted to the other side of the hub casting.
 

454cid

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Sort-of. JD7, using Hydroboost. JB7 is vacuum-boosted. At least, that's what the '97 Service Manual shows.

Oh yeah, for some reason GM did that weird. Below jb8 GM used "d" for hydroboost.

I have heard--but not confirmed--that the 3.5" x 13" drums are the slide-ons, mounted to the other side of the hub casting.

Yes, that is what i have.
 

packer0440

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I think that the 3.5" x 13" are usually just dually axles, might have changed in later years not 100%. Slide on drums might just be a model year thing. My 92 dually has the drums on the back of the hubs and they are 3.5 x 13. As far as interchangeability, I would just look at the hubs on the two. If they are the same, you might be OK to just put slide on drums on if they seat in the right spot on the backing plate.

Also I would personally just put new wheel seals in they are pretty easy to do.
 

Hoplite

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As an update, I'm pretty sure these components will not swap. I took a measurement from the end of the flange down to where the tube is mounted in the center housing and it's not the same between the two.
 
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